Abstract

The brilliancy and variety of structural colors found in nature has become a major scientific topic in recent years. Rapid-prototyping processes enable the fabrication of according structures, but the technical exploitation requires a profound understanding of structural features and material properties regarding the generation of reflected color. This paper presents an extensive simulation of the reflectance spectra of a simplified 2D Morpho butterfly wing model by utilizing the finite-difference time-domain method. The structural parameters are optimized for reflection in a given spectral range. A comparison to simpler models, such as a plane dielectric layer stack, provides an understanding of the origin of the reflection behavior. We find that the wavelength of the reflection maximum is mainly set by the lateral dimensions of the structures. Furthermore small variations of the vertical dimensions leave the spectral position of the reflectance wavelength unchanged, potentially reducing grating effects.

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A. L. Ingram and A. R. Parker, “A review of the diversity and evolution of photonic structures in butterflies, incorporating the work of John Huxley (The Natural History Museum, London from 1961 to 1990),” Philos. Trans. R. Soc. Lond. B Biol. Sci.363(1502), 2465–2480 (2008).
[CrossRef] [PubMed]

2008 (2)

A. L. Ingram and A. R. Parker, “A review of the diversity and evolution of photonic structures in butterflies, incorporating the work of John Huxley (The Natural History Museum, London from 1961 to 1990),” Philos. Trans. R. Soc. Lond. B Biol. Sci.363(1502), 2465–2480 (2008).
[CrossRef] [PubMed]

Inchaussandague, M.

Ingram, A. L.

A. L. Ingram and A. R. Parker, “A review of the diversity and evolution of photonic structures in butterflies, incorporating the work of John Huxley (The Natural History Museum, London from 1961 to 1990),” Philos. Trans. R. Soc. Lond. B Biol. Sci.363(1502), 2465–2480 (2008).
[CrossRef] [PubMed]

Parker, A. R.

A. L. Ingram and A. R. Parker, “A review of the diversity and evolution of photonic structures in butterflies, incorporating the work of John Huxley (The Natural History Museum, London from 1961 to 1990),” Philos. Trans. R. Soc. Lond. B Biol. Sci.363(1502), 2465–2480 (2008).
[CrossRef] [PubMed]

Philos. Trans. R. Soc. Lond. B Biol. Sci. (1)

A. L. Ingram and A. R. Parker, “A review of the diversity and evolution of photonic structures in butterflies, incorporating the work of John Huxley (The Natural History Museum, London from 1961 to 1990),” Philos. Trans. R. Soc. Lond. B Biol. Sci.363(1502), 2465–2480 (2008).
[CrossRef] [PubMed]

Figures (6)

Overview of the FDTD simulation setup. The green framed part on the left side corresponds to the actual simulation area. The system is periodic in the horizontal direction, continuously repeating the structure. The boundary condition (BC) in vertical direction is absorbing (perfectly matched layer, PML). A source emitting a transverse magnetic wave illuminates the structure from above. The direction of the electric field (E) is highlighted with a green arrow, the direction of incidence with a red arrow. The reflected light is detected at each wavelength. For a detailed explanation of the geometry parameters five additional structures are displayed in the right part of the figure.

Transformation of a planar layer system to the final shelf-structure. The simulation region is indicated with a green rectangle. The planar layer system (a) is cut into two halves and a vertical offset “shelf offset” is introduced (b). Afterwards the distance of the structure to the simulation region (corresponding to the parameter “structure distance”) is increased (c) and the shelves are separated in horizontal direction (d). To reach the final “bookshelf structure” the height of the central pillar is increased (e). In (f) the offset of the shelves was varied once more this time for the final structure.

The resulting reflectance spectrum of the optimization process for the color blue (a) shows a sharp reflection peak at 445 nm at the same time suppressing the reflection in the yellow color range. In (c) the reflection spectrum at different detector angles of the Morpho rhetenor butterfly for an incidence angle of 0° is shown. The structural parameters of a Morpho rhetenor butterfly where inserted into the FDTD model (b), showing close resemblance to the experimental results (c).